The present invention generally relates to flashlights.
Conventional flashlights include a housing which is typically sized to contain two or more batteries. The housing includes a head assembly with a light source at one end of the housing and an end cap assembly at another end of the flashlight, opposite the head assembly. The central portion of the housing between the head assembly and the end cap holds the batteries and can serve as a handle for the flashlight. The end cap assembly, and in some cases the head assembly can be removed to insert batteries. When charged batteries are inserted, an on/off switch can be activated to form an electric circuit between the batteries and the light source to generate light.
Conventional flashlights are typically designed to contain batteries of only one size, that is, batteries that have the same diameter and length. These flashlights can present an inconvenience or problem if the particular size battery needed to operate the flashlight is not on hand. To overcome this problem, flashlights have been developed to house batteries of two or more different sizes, and these designs allow for an electric circuit to be established through two different size batteries positioned in a series arrangement. Such an arrangement, however, can result in a safety problem when terminals of two different size batteries contact one another. For example, when the electrical energy supplied by the smaller of the two batteries is depleted, the larger of the two batteries continues to charge and to generate internal gas within the battery due to chemical reaction. The pressure generated by internal gassing can cause battery fluid to leak from the flashlight and create a harmful situation.
In other flashlights, the housing is large enough to contain batteries of different sizes. The batteries are located in separate compartments inside the housing according to the size of the battery and different size batteries operate on separate electrical circuits. For example, in a flashlight having a housing that is sized to accommodate two C size batteries and two D size batteries, the C size batteries and the D size batteries can operate the flashlight on separate electrical circuits. The problem, however, is that such a design can require that the housing be relatively large and bulky.